One of the latest trends that does not show any sign of fizzling out yet is 3D printing. The technology isn’t mainstream enough for everyone to have a 3D printer but I’ve had many interested people when talking about the things I’ve printed. Surprisingly squirting melted plastic through a hot-end and getting a good print is hard and is more of an art form. Here are some of my learnings and tips on 3D printing.
Choosing a 3D printer
I had been trying to decide on a 3D printer for a while and did quite a bit of research beforehand. It was very tempting to get a super cheap £200 Chinese clone like an Ender or Creality however when doing my research it seemed these took quite a bit of tweaking to get right. The high-end printers such as the MakerBot Ultimaker looked very impressive but they would take up too much space in my tiny London flat, not to mention that spending over £1000 on a printer seemed expensive for a casual hobby and so I settled on the original Prusa 3 MK3S – £700 in kit form. This fantastic mid-range printer is a defacto standard. It’s open-source so many cheaper clones exist but the original has so much support and so many users that chances are if you do run into a problem, someone has encountered the same thing and posted about it in a forum somewhere. This shouldn’t be discounted because you’ll probably be searching on Google a lot! Prusa also release kits to allow you to upgrade to a future model so it makes this printer great for the future too.
The first layer
One of the most important things you’ll learn is that the first layer of plastic squirted down is the most critical. If this layer doesn’t stick to the bed of the printer it won’t be able to stick any layers down on top of it and so the print will result in a big messy blob of plastic protruding from the hot-end. I’d say that out of all my failed prints, two-thirds of them failed at the first layer stage. There is one thing you can do however to greatly improve your chances of a successful print and that is to ensure the print bed is clean. The procedure is different depending on if you’re using PLA (Polylactic Acid) or PETG (glycol-modified Polyethylene Terephthalate) plastic.
So what can you do about it? Always wash your PEI coated metal sheet gently in washing up liquid. It will attract oil, dust and dirt like a magnet and washing up liquid will remove 90% of it. However, you’ll also need to buy a big bottle of Isopropanyl of 99% strength from Amazon and a soft micro-cleaning cloth. Use this as a second treatment to remove any remaining dirt (often unseen but trust me, do this before every print – make sure the bed is cool as the alcohol will last longer dissolving any grease and dirt better.
If you’re printing using PETG you need to change tact slightly. With PLA getting it to stick on the bed can be hard, with PETG you have the opposite effect – it will stick to the bed so hard you’ll probably damage the PEI coating trying to separate the items. There are two common ways to fix this, the first is using a regular PVA glue stick and rubbing it on the bed. This works well but you have to be careful to give it an even coat and not to miss anywhere. It still might be hard to remove but since glue sticks are water-soluble, running the whole PEI sheet under warm tap water will help loosen a finished print.
The second method took me a while to perfect but works the best. You will need a bottle of standard smear-free window cleaner which you’ll probably already have. Next, clean the bed just as you did for PLA but get some kitchen roll and spray one or two squirts of window cleaner onto the roll. Make sure you only use one or two squirts. Most window cleaners have a compound that makes the window sparkle and it seems to acts as a grease. Your print just won’t stick if you use more so be conservative.
The duration of a print is affected by many things. The most common is the layer size. 0.10mm layers take considerably longer to fill the same volume as a 0.20mm layer. If you need the detail go for 0.10mm but for most things 0.15mm or 0.20mm is fine.
The infill is what goes inside a 3D print. It would take way too long to 3D print a completely solid object and so some clever 3D printing engineers came up with infill, essentially a hollow grid pattern similar to honeycomb that allows the 3D print to have strength but still be light and print quickly. There are many different patterns – rectilinear, triangles, honeycomb etc and they each affect print-time. It’s best to try a few out but in general, rectilinear tends to be faster. Also, the infill is specified as a percentage of how dense it will be with 100% infill meaning it will be solid. Often 15-25% is common. 15% will print faster but have less structural strength than say 25%.
For a typical 3D print, it will outline the current layer before infilling. The outline is known as the perimeter and is very important – it’s essentially the skin or outer shell of your 3D printed object. The perimeter tends to be created slower than with the infill because it is defining the shape of your object. Sometimes objects can be made to reduce the surface area of the perimeter which will speed up printing. For example, if you had a ring-shaped object, it would need to print a perimeter on the outer edge of the ring and the inner edge. By filling in the inner ring, the slicer software will still produce an outer ring but everything inside will be printed with an infill pattern which is usually considerably faster.
You can only print on top of the previous layer which means you can’t print in mid-air. The new layer has to overlap the layer beneath. The result is that you can’t print with an overhang of more than 45 degrees without additional help. This is where supports come in, they build a platform to prop up any overhanging layer. When the print is finished you simply snap off the plastic. They don’t always produce a clean finish though so often if you can design your printed object not to need supports or you can invert it on the print bed you’ll get a better result. Since there is less plastic being printed it will print faster.
It is possible to print multiple copies or multiple objects at the same time however any errors that happen with either object will often ruin both. E.g. since the layer from object A cannot be placed down, the plastic will stick to the print nozzle and glob on object B.
One way to avoid this is to print the objects sequentially. You’ll need to remove object A off the bed before printing object B but at least a failure in object B won’t impact object A.
Top places to find stuff to print
Designing things to print is hard and to begin with, it’s much easier to print other people’s designs. Here are a few of my favourite places:
- Prusa Community
- Hack Magazine which has a column on cool 3D printed items
Designing 3D printable objects
Creating designs is something I’ll save for another blog post but there are many good places to start learning how to use Autodesk Fusion 360 or Blender for 3D printing.
Surprisingly there is a lot of skill required to get a good 3D print. Hopefully, my tips will save you many hours! Currently, the technology is not as easy as say using a normal inkjet printer but it will evolve with time. Until then, practice 3D printing and learning, with every print you should learn something.